J/ApJ/692/1464ivo://CDS.VizieR/J/ApJ/692/1464doi:10.26093/cds/vizier.16921464CDSGeha M.Willman B.Simon J.D.Strigari L.E.Kirby E.N.Law D.R.,Strader J.2018-01-05T08:57:09Z2011-03-21T14:51:16ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frgalaxiesvisible-astronomysloan-photometryradial-velocityWe present Keck/DEIMOS spectroscopy of Segue 1, an ultra-low-luminosity (M_V_=-1.5^+0.6^_-0.8_) Milky Way satellite companion. While the combined size and luminosity of Segue 1 are consistent with either a globular cluster or a dwarf galaxy, we present spectroscopic evidence that this object is a dark matter-dominated dwarf galaxy. We identify 24 stars as members of Segue 1 with a mean heliocentric recession velocity of 206+/-1.3km/s. Although Segue 1 spatially overlaps the leading arm of the Sagittarius stream, its velocity is 100km/s different from that predicted for recent Sagittarius tidal debris at this position. Using spectral synthesis modeling, we derive a metallicity for the single red giant branch star in our sample of [Fe/H]=-3.3+/-0.2dex. We conclude that Segue 1 is the least luminous of the ultra-faint galaxies recently discovered around the Milky Way, and is thus the least-luminous known galaxy.2009ApJ...692.1464Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/692/1464CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/294 : The SDSS Photometric Catalog, Release 7 (Adelman-McCarthy+, 2009)J/ApJS/191/352 : Abundances in stars of Milky Way dwarf satellites (Kirby+,https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/692/1464https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/692/1464http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/692/1464https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/692/1464https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/692/1464http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/692/1464GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/692/1464/table2 (Keck/DEIMOS velocity measurements for stars in Segue 1 sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/692/1464/table2?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/692/1464/table2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/692/1464/table2?GETtext/xml+votable180.050000true151.6687516.0439170.0055555555555555566/4419https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/692/1464?format=asciiOpticaldefaultJ/ApJ/692/1464/table2Keck/DEIMOS velocity measurements for stars in Segue 1 samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintMmSample type (members/non-members)meta.code.membercharIDSDSS-DR6 source identification (the last seven digits of "ObjId" identifying the object)meta.id;meta.mainintRAJ2000Hour of Right Ascension (J2000)pos.eq.ra;meta.mainDEJ2000Degree of Declination (J2000)pos.eq.dec;meta.maingmagSDSS-DR6 g band magnitudemagphot.mag;em.opt.Bfloatg-rSDSS-DR6 (g-r) color indexmagphot.color;em.opt.B;em.opt.RfloatHRVHeliocentric radial velocity (1)km/sspect.dopplerVeloc;pos.heliocentricfloate_HRVError in HRVkm/sstat.errorfloatVgsrGalactocentric velocity (1)km/sphys.veloc;pos.galactocentricfloatDR7Display the SDSS-DR7 data (Adelman-McCarthy et al., 2009, Cat. II/294meta.ref.urlcharSloanDisplay the SDSS data for this starmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.refchar